I. Technical Field
Embodiments described herein relate to auto-negotiation.
II. Background Art
Computing devices and systems, such as those found in data centers and enterprise systems, use auto-negotiation protocols. Auto-negotiation is a simple, slow communications protocol that is used to initialize communications between link partners, e.g., servers, switches, routers, computer components, etc. Auto-negotiation is used to advertise link partner capabilities and to determine which communications protocols are supported by both sides of the link to provide ways to resolve capabilities to the highest common denominator between link partners. Auto-negotiation is defined in clauses 28 and 73 of IEEE standard 802.3 to connect computers, such as servers, to communication switches or routers. For instance, a data center may connect one or more servers to a switch that acts as a communication hub between the servers and a network, such as local area networks (LANs), the Internet, etc.
Prior auto-negotiation solutions use passive cables to establish the physical connections between devices like servers and switches, e.g., using twin-axial cables, etc. These passive cables typically include four channels or sets of transmit/receive wire pairs (i.e., 8 wires per connection). Given the high and increasing number of servers and connections in data centers, server farms, and enterprise systems or networks, the large amount of cabling required increases a number of operation factors such as routing difficulty, material costs, cooling costs due to heat generation, power required to drive multiple passive cables, and cable weight supported by server and switch interfaces.
Additionally, mismatches of communication protocols between legacy and state of the art devices (e.g., different data transmission rates) advertised during auto-negotiation can inhibit full utilization of communication capabilities for newer hardware and devices.
Existing active cable solutions support standard auto-negotiation protocols but do not use higher-speed signaling methods on the line side of their communication links, and therefore have disadvantages in terms of material costs, power, weight, etc. These existing solutions use equalization techniques in their signaling to enable longer communication links with existing signaling approaches.